We do our best to make Alfred as compatible as possible with older versions of OS X. As such, Alfred is compatible with OS X 10.6+ Intel Macs, however 10.8 (Mountain Lion) is recommended to take advantage of all of the current and future features.

In addition, Alfred is built on top of the OS X metadata which is maintained when Spotlight is enabled (by default) on these versions of OS X. For Alfred to be able to serve you fully, you should not turn off Spotlight indexing.